The invention relates to a procedure to manufacture a textured effect in a plastic film, and to plastic films having a relief pattern made by this procedure.
Various procedures are known to manufacture textured effects in plastic films (see the book by Otto ALTHAUS: Packaging Using Plastics, Hanser-Verlag, Vienna, 1997, pp. 219-220).
The best known and most used procedure is one in which the plastic film, preferably a thermoplastic, is passed through a pair of rollers provided with a female and a male molding surface, so that the calendered film is embossed with an imprinted texture.
A method to impress plastic film using flat heat stamps is also known. Additionally, contact-free procedures such as irradiation, heat treatment, or air pressure that create imprinted textures are known.
Chemical impression procedures also exist. For example, a film of cellulose ester may be treated at individual points using an alkali salt so that ornamental effects result in the areas treated. With this procedure, however, the treatment solution must be very thoroughly rinsed since it would lead to undesirable spot formation if it were to remain on the plastic in untreated areas.
A procedure is also known from the German Patent No. DE 690 12 344 T2 that creates a material possessing an interference pattern, e.g., a hologram, whereby one side of a base film is coated with a solvent that surrounds a transparent, heat-deformable lacquer. The lacquer is dried so that a solid lacquer layer is formed. The interference pattern is formed by impressing the interference pattern onto the side of the solid lacquer layer facing away from the base film. The base film is subsequently separated from the lacquer layer.
Another known procedure comes from JP 52-148557 in which expanding pressure paint is used that leads to a relief-type structure on a substrate after printing and expansion.
The Japanese Patent No. JP 73 29083-A describes a procedure in which a curling or crinkling effect results from partial adhesion of a material with a thinned substrate whereby a curling results at the non-adhering points after contraction. A disadvantage here is that an inconvenient procedure is involved, and that adhesive remainders may remain on the materials.
Reference is also made to a procedure to form patterns (German Patent No. DE 37 19 957 A1) in which an irradiation-absorbing material is placed into an environment of synthetic fibers and polymers of high molecular weight, whereby the material is heated by means of irradiation with infrared light, and the surrounding polymer is softened, shrunk, melted, or broken. It is possible by means of this alteration to create a crinkled or relief pattern. This known procedure for application to woven fabrics, coarse-woven material, plush (moquette), and knitted fabrics is particularly suitable. An embodiment for films is not described. A disadvantage to this type of manufacture of ornamental effects is that an optical alteration must be undertaken by means of high light-absorbing agents, soot or graphite being specifically specified, by means of which heat may be applied locally. Even if, as recommended, rinsing is performed after the irradiation treatment, undesirable color alteration cannot always be avoided.